The invention relates to document scanning systems, and more particularly to a scanning system that includes document previewing.
Copying or scanning a document on a copy or scanning system typically involves placing a document (either manually or automatically) in contact with an image capture surface. Because most copy machines and scanners accommodate different size documents, the image capture surface is usually larger than a typical 8.5 inchxc3x9711 inch (215.9 mmxc3x97279.4 mm) piece of paper. As a result of the large image capture surface, documents can be placed on the image capture surface in positions that do not correspond to the particular location required for copying or scanning, which will be referred to herein as the xe2x80x9cimage area.xe2x80x9d Documents located in the wrong position on the image capture surface result in unacceptable images that are usually discarded, wasting time and resources.
Properly locating a document on an image capture surface is further complicated when features such as magnification or reduction are utilized. When magnification or reduction features are utilized, it is difficult to determine exactly how the document fits within the actual image area, and it is difficult to determine how images on the document will appear.
In order to determine the appearance of an image before a scanned image or a copy is actually generated, it would be advantageous to have a system that enables document previewing. In conventional photo-copiers, document copying is accomplished by illuminating a document and then directing reflected light from the document onto a photosensitive belt or platen. Changes in electrical charge on the photosensitive belt or platen are then utilized to transfer toner to a new piece of paper. While conventional copiers work well for their intended purpose, they do not include sensing hardware that can be easily utilized for document previewing.
In addition to conventional copiers, systems have been developed that utilize electronic imaging techniques to copy images from documents. Systems utilizing electronic imaging have been equipped with document previewing capability. Known copy systems with document previewing capabilities are disclosed in U.S. Pat. No. 4,656,524, entitled xe2x80x9cElectronic Imaging Copier,xe2x80x9d issued to Norris et al., and U.S. Pat. No. 4,656,525, entitled xe2x80x9cElectronic Imaging Copier,xe2x80x9d issued to Norris. Both copiers of Norris utilize a photo responsive device such as a linear charged coupled device (CCD) array to capture an electronic image of the target document. The scanned, electronic image is utilized to print a copy of the target document. The electronic image is captured by passing the linear CCD array by the document in a line-by-line manner.
Previewing a document with the Norris copiers involves scanning the document with a linear CCD array to create electronic image data and then displaying the electronic image data on a display device. The Norris copiers utilize the same scanning hardware for document previewing as is used for document copying. While the previewing feature of Norris works well for its intended purpose, previewing a document utilizing the same scanning hardware as is used for document copying requires a line-by-line scan of the document. The mechanical movements required for line-by-line scanning are time consuming and prevent real-time previewing of the target document.
Known preview systems have also been applied in image scanners that are used to create an electronic copy of a document. For example, an image scanner that includes a preview system is disclosed in U.S. Pat. No. 4,837,635, entitled xe2x80x9cA Scanning System in which a Portion of a Preview Scan Image of a Picture Displaced on a Screen is Selected and a Corresponding Portion of the Picture is Scanned in a Final Scan,xe2x80x9d issued to Santos and assigned to the assignee of the present invention. In Santos, the scanner can perform either a preview scan or a final scan. The preview scan is simply a lower resolution version of the final scan. Again, the same scanner hardware is utilized to perform the preview scan or the final scan. Whether the scanner is performing a preview scan or a final scan, the scanner hardware must sweep across the document in a line-by-line manner to capture the electronic image data. Although the preview system of Santos works well for its intended purpose, the time required to scan a document limits the ability to provide real-time previewing.
As a result of the drawbacks regarding prior art preview systems, what is needed is a preview system that can display a document located on an image capture surface without utilizing the document reproduction hardware, and what is needed is a preview system that can display a document in real-time.
A document scanning system includes a preview sensor that is dedicated to document previewing and distinct from any other sensor that is involved in the document capture process. In one embodiment, the preview sensor is a two-dimensional sensor array that captures the outline of an entire document using parallel processing. The captured document outline is previewed on a display device to determine its position relative to an actual image area that is defined by the scanning system. In an enhanced embodiment of the system, the preview sensor captures an image that is on the document in addition to the outline of the document, so that the image of the document is also previewed relative to the image area. Providing a dedicated preview sensor that captures document position and image data in parallel enables real-time display of a document relative to the image area.
The document scanning system having the document previewing capability includes an image capture surface (i.e., a document scanning surface), a scanner system, a preview system and a display device. The image capture surface is preferably a conventional glass platen, as utilized in conventional photocopy machines and conventional document scanners. The image capture surface is transparent and provides a surface on which the desired document is placed for creating paper or electronic copies. Typically, the image capture surface is integrated with a cover that improves illumination of a document during copying or scanning.
The document scanning system may include a conventional scanner system, or a hybrid copy system that combines document scanning and printing to produce document copies. The conventional scanner system includes a light source and a linear photosensor array. In operation, a document placed on the image capture surface is illuminated and the linear photosensor array is scanned across the document to create an electronic copy of an image. The electronic copy of the image can then be stored in memory, displayed, printed and/or edited. As described above, known previewing techniques utilize a low resolution scan with the linear photosensor array to create a preview image.
The hybrid copy system combines electronic scanning and printing to copy a document. In the hybrid copy system, the document is scanned to create electronic image data. The electronic image data is used to drive a printer, such as a laser printer, to create a copy of the document that is located on the image capture surface.
Regardless of the type of system that is utilized to make document copies, a dedicated preview system is provided that operates in addition to the scanner system. In an embodiment, the preview system is a combination of hardware and software that is independent of the scanner system. The preview system displays, on the display device, the outline of a document that is placed on the image capture surface. In one embodiment, the outline of the document is displayed relative to an outline of the actual image area of the scanner system. In another embodiment, the preview system displays the image of the document relative to the actual image area in addition to the display of the outline of the document relative to the actual image area.
An embodiment of the preview system includes the image capture surface, a light source, optics, a preview sensor, a processing unit, and the display device. The light source provides light to the image capture surface in order to illuminate a document that is located on the image capture surface. The intensity of light required by the light source depends on whether or not the preview system is configured to display the outline of a document or the image on the document in addition to the outline of the document.
The optics preferably include a wide angle lens that enables optical energy from the entire image capture surface to be directed to the preview sensor. The display device is preferably an LCD display device that is integrated with the scanner system.
The preview sensor is dedicated to the previewing system and is separate from the sensors that are utilized in the scanner system for scanning. In an embodiment, the preview sensor includes a two-dimensional photosensor array that can capture an entire image in parallel without scanning across the image capture surface. The preview sensor is operated at a refresh rate of greater than four frames per second, and preferably greater than twenty-four frames per second, in order to display a real-time representation of the document relative to the image area. The preview sensor can be fixed with respect to the image capture surface. However, the sensor may be movable in order to accommodate for features such as enlarging or reducing.
The processing unit is preferably a hardware and software system that receives signals from the preview sensor and transforms the signals into display signals that are compatible with the display device. The processing unit can also take into account paper size and magnification or reduction in order to display a representation of the image area and the target document on the display device. The processing unit can be dedicated to the preview system or the processing unit can be shared with the scanner system.
In operation of the preview system, a document is placed on the image capture surface and the document is illuminated by the light source. Light reflected from the document is captured by the preview sensor and the preview sensor transmits image signals to the processing unit. The processing unit generates display signals and a representation of the document is displayed on the display device. The representation of the document displayed on the display device is shown relative to the image area of the scanner system. If the document is moved on the image capture surface, then the movement is shown on the display device, preferably in real-time. If the scanner system is programmed to generate a magnified copy of the original document, then a magnified version of the document is displayed on the display device relative to the image area of the scanner system. Similarly, if the scanner system is programmed to generate a reduced copy of the original, then a reduced image of the original document is displayed on the display device relative to the outline of the image area. Once the document is satisfactorily positioned on the image capture surface, as indicated by the preview system, the scanning system is utilized to generate a copy, either printed or electronic, of the document.
Because the preview system has a dedicated preview sensor, the preview sensor can be a lower resolution two-dimensional sensor array that captures images of the entire document in parallel without having to mechanically scan across the document. Capturing images of an entire document in parallel enables the preview system to display an image of the document in real-time, or near real-time. Real-time previewing enables a user to quickly preview a document while making subtle adjustments in order to generate a desired copy on the first attempt.